In the normal operation of a lathe, a workpiece is mounted with its axis coincident with the spindle axis of the lathe and is turned about said axis. A tool is moved radially into engagement with the turning workpiece and material is removed as the workpiece turns. The tool is also translated along a track parallel to the turning axis of the lathe to allow for operative engagement of the tool along the length of the workpiece. By varying the radial and lateral position of the tool, a wide variety of shapes can be obtained. In order to insure that the finished shape is symmetrical about the axis of the workpiece, it is essential that the workpiece axis be accurately aligned with the spindle or turning axis of the lathe. Generally, the workpiece is constructed with cylindrical end portions called journals and the axis of these portions are accurately located and may be engaged by the spindle. However, in certain instances, the axis of the workpiece is not obvious and the spindle cannot accurately be engaged. Also in some operations, the workpiece is supported solely from below on steady rests without help from the spindle engagement. In these instances, alignment of the workpiece and spindle axes is more difficult and additional means are required to affect this adjustment.
This adjustment was generally accomplished by the use of an appropriate gauge which would indicate position of the journal surface in relation to the spindle axis. This gauge is attached to an arm which is secured to the faceplate of the lathe for rotation therewith. In operation, the gauge would be positioned in contact with the journal surface and rotated while the workpiece is still. Deflections of the gauge would indicate a lack of concentricity between the faceplate and the journal surface. By adjusting the steady rest until there is no deflection, the axis can be aligned. However, because of the awkward position of the gauge, adjustment of one end continuously requires readjustment of the opposite end gradually minimizing the deflection until it is zero. This operation may take hours to accomplish, due to the cumbersome and inaccurate nature of the gauge assembly. In many instances, the alignment process may take longer than the actual turning operation.
The indicator of the subject invention is more accurate, and easier to handle and results in a substantial reduction in the time needed to set up and align the axis of the workpiece with the spindle axis of the lathe.